Amorphous silicon is a material applied in various electronic devices such as solar cells, metal-oxide-semiconductor field-effect transistors, image sensors, and micro-electro-mechanical systems. As an example, a transistor may be formed by stacking a metal layer, an oxide layer, and a semiconductor layer together. An amorphous silicon layer can be used to form a gate structure of a transistor. The amorphous silicon gate can prevent current leakage that occurs in the conventional techniques.
An amorphous silicon layer may also be deposited on a surface of a substrate to form a crystallized silicon film. The surface of the substrate may be silicon, silicon nitride, or silicon oxide. An amorphous silicon layer may also be deposited on the surface of metal layers, such as aluminum or chromium, or an organic material such as polyimide.
An amorphous silicon layer may be formed by chemical vapor deposition (CVD) such as plasma enhanced CVD (PECVD). It may be problems in the deposition of an amorphous silicon layer to keep a stable thickness and maintain particle free for the amorphous silicon layer. Particle free amorphous silicon layer with a stable thickness can reduce the thermal stress which is the root cause of crack and peeling. Therefore there is a need to improve the stable thickness and maintain particle free in the deposition of an amorphous silicon layer.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.